Automatic draft control for furnaces



July 1, 1930. 'i= DAVI-SON 1,769,497

AUTOMATIC DRAFT CONTROL FOR FURNACES Filed May 14, 1929 I I4 Januanlluv- 2 Frederimk Damscln Patented July 1, 1930* d d i I UNITED STATY PAT N oFicE;, FREDERICK DAvIsoN, or sunisuns rfonremo, CANADA; I r

AU'roM'A'rIo DRAM; contract roa runn'nons My invention relates to improvements in draft controls for furnaces, and the object of my invention is to'construct a naturaldraft control device particularly adapted for furna ces in which an artificial air draft is incorporated, so that passage of natural draft through thefire box may be controlled in accordance withthe artificial draft pressures.

A further object of my invention is'to so construct my device that its attachment and application willin no way interfere with standard furnace construction or necessitate any extensive alterations when being attached.

My invention consists of a draft control constructed and arranged all as hereinafter more particularly described and illustrated in r the accompanying drawings, in which Fig. 1 is a perspective view of a fragmentary portion of a furnace casing, showing a I blower fan positioned exteriorly thereof, and my device positioned in proximity to the fire box door.

Fig. 2 is an enlarged front elevational view 5 of a portion of the furnace casingsurrounding the fire box door showing my device positioned upon the door.

Fig. 3is a horizontal cross sectional view taken through the line 33, Fig. 2, and

, 3o 7 Fig. 4 is an enlarged view of a fragmentary portion of the air blast conduit showing the pipe connection which extends therefrom to my device.

Like characters of reference indicate corresponding parts in the different views.

As hereinbefore explained my device is par ticularly constructed for use upon furnaces of the type illustrated in Fig. 1 in which an artificial air draft is created by means of a blower fan 1 and conduit 2, extending therefrom to the furnace A; An artificial air draft is generally used in conjunction with 11 by meansof a pair of hinges19. When and smaller grades of coal. All these types of furnace permit the entry of a natural draft 7 during the period that the artificial draft is passingthrough the furnace, but it has been found, particularly in the case of oil furnaces automatically controlled by axthermostat, that when'a suf icient degree of heat has been obtained whereby the actuationof the oil burning mechanism and blower fan is cut off that r the natural draft continues to'pass through the heated furnace and much more rapidly cools itdown to the burner actuating temperaturethan would be the case if this natural draft were cut ofi during the periods of inaction. J Y

In orderto accomplish 'this I have constructed-the device illustrated inthe drawings, and which consists'of a cylinder 3 mount edupon a right angle bracket 4:"Wh10l1 is secured to thelfurnace door 5 by means'of bolts 6. Interiorlyof this cylinder 3Iiposinon a piston and. piston rod 7 andL-B, the piston rod'projectingthrough anlorificef9. in

the rear' 'end 1O of the cylinder,'iand having its outerend in contact with the casing '11 of the furnace door. 12 is a lielical springextending between the cylinder and; the *furnace casing. i Centrally of the outer end 13 V of the cylinder I furnish a nipple 14 connected to-a flexible .piipeilowh-ich extendstherefrom through an orifice 169i11t0 theinterior of the=airconduit 2. The end 17 of the pipe ;15 faces'the direction offlow ofthe artificial draft indicated by arrows in Fig. 4;, the end ofv the pipe I being slightly bell mouthed.

' Thefurnace door 5 illustrated in the drawings is I'ofcourse of the standard type-ggenerally provided with an artificial. air draft damper 18, and mounted upon the door frame my device isused'in combination witha furnace door of the type illustrated inthe drawings whereinthe damper 18 isinc'orpora'ted, "suchdamperis kept closed and the passageof natural -draft'is controlled by opening and 9o n t0;be.unfierSbOOdthatinthepiston andcyl inder asse nhly the jfpiston isprovided with pistonringsajnd the cylinder withpack if =endsl 0:an-d' 13: which are threaded there.-' o unto. i l I My device operates -as follows :-1- y f "?When, the blower fa 1 isinactive'there 1b! l. a v

furnace'door fi sfkept closed-through the ings 21" between the cylinder proper and its isno'airpressure*in the lcondiiit 2,1and the 7 medium of the sprin'g112 connectedto the jryhndere which amounted upon the deer,

' the, fnrnacedoor being "in; the position; illusa e trated in Fig. 3 andythepiston-,T attheouter? p V i i i L hen the blower fan lis actuatedbyrneansv the cylinder, a piston rod extending through one end of the cylinder and engaging the fur nace casing, the cylinder and piston rod being tending fromthe artificial air draft producing means to the other end of the cylinder ilwhereby the cylinder is movedin one direcsubstantially at right angles to the furnace casin'g when the. door is closed, a'pipe line ex-' tion to open the door under-the artificial air draftpressnre, and resilient means" acting draft pressure for against the} artificial air closing thedoor. V Y 1, cf FREDERICK DAVISON.

or the eleotricalmot-or22 a air pressureis i i i u g nipple Hintofthjeouteriendofthecylinderv created intheconduit 2,1such air. pressure in turn passing along thelpipe 1:5 throngh the This air pressnrewtendstOiIllOVG the piston the piston ,1lin itself"cann-ot ino'veand the r cylinderS forthermoyes outwardly andopens "I 1 t j 1 comes ina'ctive the airpressure in conduit and;pipelfireturnstonormal and theiurnace theurnaceido0r 5againsttheresiliencyiof;;i theSpring lQLJiThedegreeofthedoorxopen w I 'ing c'being *ofyconrse. dependent nponvtheair V rearwardly'towardsfltheZfurnace; bnt'as'the i i piston rod 58 isingcon'tact with the door frame;

pressli-re'inthe oonduitZ; When the fan bespring 12f 13;. From the foregoing descriptionitwill be apparentrlthat lihaveadeyisedfa particularly a 'sinipleandefiicientde icefor eontr'ollingfthe i l a passage.ofnatnral draft thron gh a furnace, I l

late'd inaccordance Withithe artificial-- damper; controllingthei passageof natural i" draft to a hfnrnace itcbein onlynecessary to moire the damperfinsone lrectionnnder the otherdirection by resi1ient means on a second pistonor theflli-key 1 p influenee-ofitheipiston"(and niovjit inhale" I is; to he, alsoi nndgerstood V i haveshownrand described apistonr-and cylinffl h v deras;thecontrollingmeansactnatedfbyitheair pressnre ofjthe a-rtilicialggdraft,that l can Y 3 nseanywothersiinflarnieansfactuatedby .varlv V 1 ationsrin; pressiirewithout dep arting from the pended cla1 gAf deyiceforicontrolling thegnatural draft" 4 effthroiigh'swingablefurnacedoors iniiilrnaces ispirit ofimyinyention asj-set'lfor'th inithe apa, l

incorporating an rartif icial airdraft Iproyid- 7 King neans,""compr 1s1ng: a cylinder rlgldlyz vmm d ifi lfnacldoor a piston in I 

